STDs (venereal disease) are traditionally thought of as diseases transmitted through the act of sexual intercourse, with the main lesions occurring in the genital area. Including syphilis, gonorrhea, soft chancre, venereal lymphogranuloma and inguinal granuloma five kinds. First, allergic diseases: after taking drugs allergy, can cause the glans foreskin fixed rash; drug or food allergy can also cause severe edema of the foreskin; contact with topical drugs, contraceptive tools or diapers and other triggered contact dermatitis, such as the local occurrence of erythema, pimples, blisters, vesicles or ulcers; individual women allergic to semen can occur vaginal itching or vulvar urticaria. Second, traumatic diseases: abrasions and hematoma during sexual intercourse; after sexual intercourse due to temporary obstruction of lymphatic vessels can cause the dorsum of the penis or the coronal groove of the cartilage-like hard cord, within a few weeks can disappear on its own, this disease for the penis sclerosing lymphadenitis; prolonged sexual intercourse can cause edema of the genitals; the foreskin can not be reset after the foreskin is turned over, which can cause the foreskin and the end of the penis, known as the incarcerated foreskin severe edema; the bites of insects can also cause Redness, swelling and blisters in the genital area. Third, non-sexually transmitted infections: when the rotting material in the lower part of the genitals parasitizes Bacillus vulgaris, it can cause acute female genital ulcers; 2-3 days after sexual intercourse, due to the infection of the bacillus of prepuce scale or the spirochete of Fensen Pressure or the clostridium difficile, it can also cause vesiculobullous glans phocomastitis. Fourth, pre-cancerous diseases and malignant tumors: white spots and hypertrophic erythema occurring in genital area, especially those who show keratinized roughness, desquamation, warty proliferation and stubborn ulcers, may be pre-cancerous diseases or malignant tumors. Fifth, benign tumors or superfluous organisms: genital area is also common to some slow-developing, persistent and rash or small nodules, black, yellow, red or skin color. Its foci may be pearly penile papulosis, cornus, nevus, epidermal nevus, superficial lipomatous nevus, cutaneous endometriosis, vestibular gland cysts, sebaceous cysts, multiple lipid sacs, lipomas, papillary sweat gland tumors, hemangiomas, smooth muscle tumors, fibromas, or cutaneous lymphoblastomas. Sixth, other diseases: there are some complex causes or so far the etiology of the disease is unknown, the same can also lead to genital parts or systemic lesions, such as penile cavernous sclerosis, plasma cell glans, occlusive dry glans, mica and keratinized pseudoepithelioma glans, female pubic atrophy, penile dryness, sclerosing atrophic tessera, lichen planus, eczema, seborrheic dermatitis, neurodermatitis, psoriasis, pemphigus, etc. In addition, sexually transmitted infections are easily confused with common skin diseases and should be distinguished.